Magnetic ion Fe and Ni doping in the Cu-O chain and the CuO/sub 2/ plane in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta//: a positron study

Fe and Ni substitutions in the Cu-O chain and the CuO/sub 2/ plane are studied by positron lifetime experiment. Change of lifetime parameters is given and local electron density is evaluated as a function of substitution content. The results show fantastic and opposite behaviors for Fe and Ni substitutions. A strengthen effect of the localized carriers in the CuO/sub 2/ planes for Ni substitution and electronic weak localization in the Cu-O chains for Fe substitution are found in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconducting systems. The positron distribution and the annihilation mechanism are also discussed.